Motorized vehicles, and, in particular, marine craft, typically employ a hull-mounted fuel tank to store a supply of liquid fuel for the engine. Marine fuel tanks in general have a fill tube formed on the tank to enable filling of the tank with liquid fuel. These fill tubes are sealed off with a cap to prevent the entry of contaminants into the tank and to prevent the escape of liquid fuel and vapors. To maintain atmospheric pressure in the tank, a fuel tank vent line is installed having one end opening into the top of the tank and the other end opening to the atmosphere. The vent line permits fuel to be added to or removed from the tank without meeting resistance from positive or negative air pressure, respectively. In addition, the fuel tank vent line prevents the dangerous buildup of fuel pressure in the tank.
One major drawback to the present configuration of fuel tank vent lines is the unintentional overboard venting of fuel through the vent lines. This situation frequently occurs when refueling the inboard fuel tanks in marine vessels. During the refueling process, the rush of incoming fuel displaces vapor from the head space of the fuel tank into the vent line and then out to the lower pressure of the atmosphere. As the tank becomes full, this displaced vapor carries foam and liquid fuel through the fuel tank vent line where it is discharged overboard into the water or on to land. Needless to say, this is not only embarrassing to the boat owner, but, more importantly, it is detrimental to all forms of life, including water fowl and marine life.
A number of government and private organizations regulate the construction and use of marine craft. Among these organizations are the United States Coast Guard, the National Marine Manufacturers Association, and the American Boat and Yacht counsel. With respect to the latter, all manufacturers of marine pleasure craft that belong to the American Boat and Yacht Counsel and that wish to display and advertise the approval of the American Boat and Yacht Counsel must comply with its standards known as H-24 and H-33, "Gas and Diesel Fuel Systems," respectively. Proposed revisions to these standards include the requirements that any fuel tank vent line separator used with a marine fuel tank system must be independently mounted and permanently installed; have means to contain and return liquid; continuously vent during normal operation; and allow venting of liquid fuel at pressures greater than 2.4 pounds per square inch. The main thrust of these proposed regulations and requirements is the continuous maintenance of safe pressures in the fuel tank to prevent the dangerous buildup of vapor and resulting explosion.
While there are a number of devices that are designed to separate liquid and recover vapor, there are none known in the art that are specifically designed for installation in a fuel tank vent line to vent the fuel tank to the atmosphere while preventing the overboard venting of liquid fuel. For instance, U.S. Pat. No. 3,981,156 issued to Modisette et al, is directed to a vapor recovery system utilizing a vapor scrubber that recovers storage tank exhaust vapors into a closed system by absorption in a refrigerated spray. As such, the device of Modisette et al is designed to prevent the exhausting of any vapor to the atmosphere. This is unsuitable for applications to fuel tank vent lines. U.S. Pat. No. 4,769,050, issued to Shaw et al, discloses a liquid separator assembly for separating liquid from a liquid-entrained vapor. This assembly is integrally formed with a fill tube that has an enclosed containment chamber formed thereon. In this assembly, an oil fill tube is used to function as the crank case vent tube. A separate vent line is not desirable since oil is not added at the high volume and high rate that fuel is added to a fuel tank, and crankcase lubrication oil is not as easily combustible as liquid fuel. While this may be suitable for its purpose, it would not function to separate fuel and vapor in a fuel tank vent line where fuel is being added at a high volume and rate and to maintain continuous venting under normal operations.
Finally, U.S. Pat. No. 4,809,863, issued to Woodcock et al, teaches a fill neck assembly for an on-board refueling vapor recovery system. The fill neck assembly includes a space formed between the interior of an outer hose and the exterior of a fill pipe that constitutes a passageway through which fuel vapor flows from the head space of a fuel tank into a vapor flow passage and thence to a vapor canister. Within the passageway is mounted a float ball and a valve seat for preventing the flow of liquid into the refueling vapor canister from the vapor flow passage. During refueling, should liquid fuel back up through the vapor passageway, the ball will seat in the valve seat, preventing the flow of liquid and vapor. As a result, vapor and liquid is entrapped in the vapor passageway and it is unable to be directed into the fueling vapor canister. In this situation, pressure will continue to build until it is released by a breech in the system. This could easily result in an explosion.
Consequently, there is a need for a device that can be easily and quickly retrofitted to existing fuel tank vent lines as well as installed on future fuel tank vent lines and that continuously vents during normal operation and refueling while preventing the discharge of fuel into the environment.